| 摘要 |
In a system for displaying the net distance travelled by a magnetic recording tape, the tape includes a recorded track having a periodic flux pattern. During each period, the flux pattern includes an asymmetrical pulse characterized by a flux increase during a first length of tape and a flux decrease of the same magnitude during a second and different length of tape. A single flux responsive head detects the pulses when the tape is moved and a differentiating circuit provides a pulse signal whose sense is related to the directions of travel of the tape. The pulse signal is coupled to an up-down counter which drives a display. The display indicates the net distance travelled by the tape.
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